|Keep It Simple, Stupid|
I would recommend WebGUI especially for non-technical end-users. If you get through Fortune 500 orineted web site at PlainBlack's site (which turned me down couple of times), you will get GPL licensed CMS which has nice and knowledgable user community.
I would also stress difference between dynamically generated sites and ones that are baked. For sites that can use it, I would recommend baking: creating static html pages when content is edited is nice way to allow multiple mirrors or load balacing (and without need to rent database from provider). It also plays nice with proxy and caches (allthough most CMS software also do a good job at sending correct expire headers). For sites which aren't baked, you have to do black magic if you want to scale-out them to co-location facility.
There is also nice site for comparison of Open Source CMS systems (not only perl) called CMS matrix.
Full disclosure: I'm not affiliated with PlainBlack or WebGUI, but I wrote nice add-on described at node RFC: Fuse::DBI - mount database as filesystem which actually enabled me to use it :-)